Scans and tests Heather Welford As part of your antenatal care, you'll be offered a range of checks, tests and assessments to monitor you and your developing baby.

In this article

How scans work When you'll have a scan Blood tests Blood pressure checks

Weight Urine tests Palpation

Doppler test Less routine tests Are tests risky?

Your first antenatal check-up

This is likely to be the longest one. It will take place between the eighth and 12th week of pregnancy, and you'll be examined by a doctor and a midwife. You may also be offered the chance to see your baby for the first time with an ultrasound scan.

If you're working, you're legally entitled to paid time off for your antenatal care.

An ultrasound scan uses high-frequency sound waves, which bounce off solid objects. This creates a screen image of your uterus and nearby organs, as well as your baby, the baby's organs and the placenta.

Scans can be two-dimensional, three-dimensional (for better clarity, to allow easier diagnosis of anomalies such as a cleft palate) or four-dimensional (available privately).

This differs according to local policy and your own needs. Ask your doctor or midwife what your options are and what they're looking for each time.

You might be offered a scan at any of these following times:

• About six to eight weeks to confirm/date the pregnancy, see if it's ectopic (developing in the fallopian tubes, not the uterus) and check the foetus is alive by looking for a heartbeat
• About ten to 14 weeks to confirm/date the pregnancy, see if you're expecting twins, or more, and when offered alongside a nuchal scan (which looks at a pad of skin at the back on your baby's neck) assess the risk of Down's syndrome or other chromosomal conditions
• About 20 to 23 weeks to check for spina bifida and other possible abnormalities, look in detail at your baby's major organs and skeleton, check the health of your placenta and monitor your baby's growth

Later scans monitor your baby's growth and check the position of the placenta and your baby

Can I find out my baby's sex?

It's often possible to tell the sex of your baby around mid-pregnancy. You might be asked if you want to know, but some hospitals have a non-disclosure policy. Remember it's not 100 per cent reliable.

Getting ready for your scan

For external scans in early pregnancy you'll be asked to drink lots of water so your bladder pushes the uterus upwards for a better picture. Early dating scans can also be done internally. If this is the case, you won't need to drink water first as the internal scan-head rests against the uterus itself.

How external scans are done

While you're lying down, the operator (usually a sonographer or radiographer) spreads gel over your tummy and rolls a hand-held transducer across the area. The images are transmitted to a screen. These may be printed out and a copy kept with your notes. You may also be given a print, although you may have to pay for this. Some scans can be put on to a CD.

Normally, a small sample of your blood is taken at your first antenatal appointment. You may also be asked to give a sample in later pregnancy. The first test can:

• Identify your blood group
• See whether your blood is rhesus positive or negative
• Check for conditions that could affect your health or your baby's (this may or may not include HIV)
• Check your immunity to rubella (German measles)
• Check for anaemia

The blood test shouldn't be painful and should only take a minute or so. There may be slight bruising for a couple of days.

Blood tests can also be used to estimate the risk of Down's syndrome. A blood sample is taken at about 16 weeks to measure three substances: alpha-fetoprotein (AFP), unconjugated oestriol and human chorionic gonadotrophin. Together with the mother's age, these give an estimate of risk.

The level of AFP can also be used to assess the risk of a neural tube defect, such as spina bifida.

Your blood pressure will be monitored at your antenatal appointments to look for signs of pre-eclampsia, or pregnancy-induced hypertension.

You'll probably be weighed near the beginning of your pregnancy. Some, but not all, antenatal clinics weigh you at every appointment.

You'll be asked to bring, or produce, a urine sample to your antenatal appointments. Usually, a testing stick will be dipped into this to see whether protein or sugar is present. Protein can be a sign of pre-eclampsia, while sugar in urine is a symptom of gestational diabetes. Urinary tract infections may also show up on the test, and new guidelines from NICE now recommend that for every woman a urine sample should be sent to the laboratory early in pregnancy to check for the prescence of bacteria, even if the woman does not have any symptoms of an infection, because undiagnosed infection can lead to complications.

This is a manual feel of your abdomen to gauge the height of your uterus and how the baby is lying.

This is a test to listen to your baby's heartbeat and can be done throughout pregnancy by a doctor or midwife.

• Chorionic villus sampling (CVS) - tests a sample of the placenta, taken with a needle inserted through the abdomen or via the cervix. It's done at about 11 to 14 weeks and looks for chromosomal abnormalities.
• Amniocentesis - a sample of the amniotic fluid surrounding the baby is taken by syringe. Cells from the baby found in the fluid are tested for chromosomal abnormalities such as Down's syndrome. This is done from about 18 weeks and is offered to women who are at high risk.
• Mouthwash test - this can reveal if you're a carrier of cystic fibrosis (offered only in some areas).
• Nuchal fold test - this uses ultrasound scanning to measure the nape of the foetus's neck. The measurement can help to estimate the risk of Down's syndrome.

You may also be offered a blood test to check for past or present infection with the cytomegalo virus (CMG virus) and for toxoplasmosis.

Invasive tests such as CVS and amniocentesis do carry a risk of miscarriage, which you should discuss with your doctor.

Other risks are more difficult to quantify. Will the test mean you're unable to enjoy your pregnancy, or would you prefer to know everything you possibly can? Will the test give a false sense that everything's guaranteed to be OK, or will knowing that everything's fine help to reduce your anxiety?

Talk it over with your partner, other parents-to-be, your midwife and doctor.

What's rhesus negative blood?

Most people (80 per cent) have rhesus positive blood; the remainder have rhesus negative. Being rhesus positive means that the person has a substance called D-antigen on the surface of their red blood cells (this characteristic is inherited).

If the mother is rhesus negative and the father is rhesus positive, and they have a baby who inherits rhesus positive status from the father, this can result in harm to the baby

When both partners have the same rhesus factor, there's no problem, and neither is there a problem if the mother is rhesus positive and the father is rhesus negative. But if the mother is rhesus negative and the father is rhesus positive, and they have a baby who inherits rhesus positive status from the father, this can result in harm to the baby.

During the pregnancy or birth, small amounts of the baby’s rhesus positive blood may cross over into the mothers bloodstream. The D-antigen on the blood cells can then trigger an immune response in the mother, causing her to produce antibodies against D-antigen. The mother is then said to be “sensitised” to rhesus factor.

During a first pregnancy this may have no obvious effect, as sensitization don't usually happen until late in the pregnancy or at the birth. But if she becomes pregnant again with a rhesus positive baby, these antibodies can cross the placenta and attack the developing baby causing haemolytic disease of the newborn, anaemia and jaundice, which can be fatal for the unborn child. It is estimated that every year in the UK about 50 babies are lost during pregnancy or in the first week after delivery due to rhesus disease.

But these deaths can be prevented. Treatment (also known as Routine Antenatal Anti-D Prophylaxis or RAADP) consists of injections of an immunoglobulin (or antibody) against D-antigen, which prevents the immune reaction to the baby’s rhesus positive

Disclaimer: The BBC Parenting site is provided for your general information only. The information contained on this site should not be treated as a substitute for medical, legal or other professional advice. The BBC is not responsible or liable for the contents of any websites of third parties which are listed on this site.